1. Field of the Invention
The present invention relates to a pattern recognition apparatus which can recognize a pattern such as speech with high accuracy.
2. Description of the Related Art
There has been successfully made a pattern recognition apparatus in which an uttered speech is vectorquantized and a quantized code sequence is recognized by a HMM (Hidden Markov Model).
However, in the vector quantization, since a simple distance measure is normally used, the performance of HMM is reduced by a quantizing error. Moreover, the use of continuous output probability distribution has been reviewed in order to reduce the quantizing error. However, there is a problem in that the use of the continuous output probability distribution is very difficult to be put into practice since the amount of calculation is increased.
Though this is not a technique using HMM, U.S. Pat. No. 4,888,823 discloses a system wherein a LPC (Linear predictive coding) analysis of an input speech is performed, a phonetic segment sequence in 1st place, that is, label sequence, (hereinafter called as PS sequence) is learned, and the speech is recognized. The content of U.S. Pat. No. 4,888,823 is incorporated into the specification of this application for reference.